Reservoir system quality prediction

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Exploring for Oil and Gas Traps
Series Treatise in Petroleum Geology
Part Predicting the occurrence of oil and gas traps
Chapter Predicting reservoir system quality and performance
Author Dan J. Hartmann, Edward A. Beaumont
Link Web page
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The economic success of any prospect ultimately depends on reservoir system performance. The reservoir system controls two critical economic elements of a prospect: (1) the rate and (2) the amount of hydrocarbons recovered. In geologic terms, pore type and pore-fluid interaction are the most important elements determining reservoir system performance.The interrelationship of reservoir porosity, permeability, thickness, and lateral distribution determines reservoir system quality. Although quality prediction is most effective with large amounts of superior data, useful predictions can still be made from very limited data. This section discusses methods for predicting the quality of sandstone and carbonate reservoir systems.

Sandstones vs. carbonates

Sandstones and carbonates are the dominant reservoir rocks. Although quite similar, they are different. The table below[1] compares variables affecting reservoir system quality for sandstones vs. carbonates.

Variable Sandstones Carbonates
Sediment composition High variability (depending on provenance and depositional environment) Low variability [variations of limestone and dolomite ]
Cement mineralogy Quartz, calcite, dolomite, clay, and anhydrite, etc. Aragonite, high- and low-Mg calcite, dolomite
Original pore geometry Intergranular Intergranular predominates, but intragranular is important
Ultimate pore geometry Intergranular = intercrystalline > moldic Intergranular = intercrystalline = moldic > microporosity
Uniformity of pore size, shape, and distribution Fairly uniform within a facies Ranges from fairly uniform to extremely heterogeneous, even within a facies
Influence of diagenesis Minor to major Usually major

See also

References

  1. Choquette, P., W., Pray, L., C., 1970, Geologic nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, vol. 54, no. 2, p. 207–250. Classic reference for basic concepts regarding carbonate porosity.

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Reservoir system quality prediction
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